1. Field of the Invention
The present invention relates to a method of, and an apparatus for, agitating a treatment liquid in which the treatment liquid (in this specification, the treatment liquid means a liquid to be treated or processed) which is made up of a combination of a liquid and a liquid, or a liquid and a powdery material is extremely finely pulverized for dispersion and emulsification.
2. Description of Related Art
In a conventional agitating apparatus, there is provided a turbine (or a turbine wheel or agitating blades) in the center of an agitating vessel, and a treatment liquid is agitated by the turbine for further pulverization. FIGS. 5A and 5B represent examples of conventional apparatuses. In the example shown in FIG. 5A, there is provided a shaft b so as to extend into a vessel "a" and a turbine c of a smaller diameter is attached to the shaft b. The shaft b is rotated to agitate the treatment liquid d. It is thus so arranged that the treatment liquid d is sheared and dispersed by the turbine c and, at the same time, a circulation in the outward direction as shown by arrows is caused to occur in the upper and the lower portions of the turbine to thereby agitate the treatment liquid d. In order to prevent the treatment liquid from circulating without agitation, a stator f in the form of a rib is provided inside the vessel "a". In this apparatus the diameter D.sub.1 of the turbine c is relatively far smaller than the internal diameter D of the vessel "a", and is generally below one-fifth of the internal diameter D. In this Figure, reference character a.sub.1 denotes a jacket or sleeve to flow therethrough a medium for heat-exchanging purpose, i.e., for heating or cooling the treatment liquid d.
In the example shown in FIG. 5B, there is used an inclined turbine c.sub.1 as the turbine, and stators f.sub.1 are supported by means of fixing members g. This apparatus corresponds to the one as disclosed in Japanese Published Examined Patent Application No. 7913/1994. The shaft b is driven at a high speed to rotate the turbine c.sub.1 at a peripheral velocity of about 15 m/sec. It is thus so arranged that, aside from the shearing effect, cavitation is positively caused to occur on the rear surface of the turbine c.sub.1 to thereby accelerate the pulverization. The treatment liquid d near the turbine c.sub.1 is circulated in the direction as shown by arrows e.sub.1.
This kind of conventional apparatuses have the following disadvantages.
1) The treatment liquid d which is subject to the function of the turbine c, c.sub.1 is limited to that which is present in the neighborhood of the turbine c, c.sub.1. Although the function of the turbine c, c.sub.1 is equalized by the circulation of the treatment liquid d as shown by the arrows e, e.sub.1, it is necessary to increase the number of circulation in order to treat the entire treatment liquid d, with the result that the time required for treatment becomes long.
2) Rotation of the treatment liquid d together with the turbine c, c.sub.1 reduces the agitating effect. As a solution, stator(s) f, f.sub.1 must be provided as shown in FIGS. 5A and 5B.
3) If the turbine c, c.sub.1 is rotated at a high speed in order to give a higher energy to the treatment liquid d, there occurs a slipping phenomenon accompanied by cavitation when a certain speed of rotation has reached. In particular, when a liquid of high viscosity is to be agitated, the agitation effect is extremely reduced due to the above-described slipping phenomenon.
4) There are many occasions in which, during the processing work, the treatment liquid d is agitated, charged, or discharged while the treatment liquid d is heated or cooled by flowing a medium for heat exchanging through the jacket a.sub.1. However, since the overall speed of circulation of the treatment liquid is low, the temperature distribution inside the vessel "a" becomes uneven, with the result that the agitation by the turbine c, c.sub.1 at a uniform temperature is difficult.
In order to improve the above-described conditions, there has been used an apparatus in which auxiliary devices such as an agitator, a scraper, or the like are added. However, the above-described arrangement results in a complicated mechanism, and a satisfactory effect cannot be obtained.
As a further disadvantage of the conventional apparatus, the following can also be pointed out.
5) Agitation to attain the pulverization, dispersion, and emulsification of a high order cannot be performed by the change in the shape of the turbine or by the addition of the above-described auxiliary devices. Such an arrangement does contrarily increase the amount of adhesion of the treatment liquid to various portions of the apparatus, resulting in a smaller yield. Further, the turbine c, c.sub.1 must be set to an appropriate height because the circulation of the entire treatment liquid becomes poor if the turbine c, c.sub.1 is positioned too close to the bottom of the vessel "a". Then, the minimum amount of treatment liquid cannot be decreased, resulting in a poor payability or poor economy. Further, if the agitator, the scraper or the like are added, the structure becomes complicated and the ease with which the apparatus can be flushed or cleaned becomes poor.
The present invention has an object of providing a method of, and an apparatus for, agitating a treatment liquid which solve the disadvantages mentioned in the above items 1) through 5).